The present disclosure relates generally to a medical device for transporting fluids. More particularly, the present disclosure relates to a catheter for transporting fluids from the patient's body for extracorporeal treatment such as dialysis, and returning treated fluids to the body.
Dual lumen catheters are commonly used for transporting body fluids for treatment, such as dialysis, external of a patient's body, a process generally referred to in the medical field as “extracorporeal” treatment, and thereafter returning the treated fluid to the body. The fluid is withdrawn from the body through one of the lumens of the catheter, generally referred to as the withdrawal or aspiration lumen. The fluid is subjected to a treatment process, and thereafter returned to the body through the other lumen, generally referred to as the infusion or return lumen.
In many cases, the extracorporeal treatment is carried out as part of a hemodialysis procedure. During hemodialysis, blood is withdrawn from a blood vessel through the aspiration lumen and routed to a dialyzer for cleansing. The cleansed blood is then returned to the vessel through the infusion lumen. When such a catheter is used for hemodialysis, whether for short-term hemodialysis (generally thirty days or less) or longer-term hemodialysis (generally greater than thirty days), it is generally inserted into the body through the internal jugular vein, subclavian vein or femoral vein. In addition to hemodialysis, extracorporeal catheters can also be used for other procedures, such as pheresis and hemofiltration, in which a fluid is removed from the body for treatment and later returned to the body.
Among the types of commercially available dual lumen catheters used for dialysis are dual D-shaped lumen catheters and coaxial catheters. In some instances, dual D-shaped lumen catheters may be more undesirable. For example, for a given pressure, the rate of fluid flow through a D-shaped lumen catheter is typically less than the flow rate for a circular cross-sectioned lumen in a coaxial catheter of comparable area. One reason for this pressure disadvantage is that there is generally more turbulence and backpressure generated through a D-shaped lumen catheter. Moreover, internal crevices of a D-shaped lumen catheter can increase the risk of blood clot formation.
Recirculation of treated fluid is another factor to consider for dialysis catheters. Recirculation is problematic when a majority of untreated blood that is aspirated through the aspiration lumen is the same fluid that was just previously treated and returned to the body vessel. As a result, the overall duration of treatment is lengthened, thereby inconveniencing the patient.
In regard to dialysis coaxial catheters, some coaxial catheters for use in dialysis can have a freely dangling inner catheter at the distal end of the outer catheter. Consequently, vacuum used to withdraw fluid may tend to pull the inner catheter toward the interior wall of the outer catheter, thereby undesirably occluding inflow side ports that are formed in the outer catheter wall. Once flow is partially occluded in a manner to sufficiently affect the inflow hemodynamics, the dialysis treatment suffers and the treatment is lengthened. Furthermore, the formation of fibrin sheaths along the inflow side ports can also cause undesirable occlusion. Fibrin sheaths are formed, e.g., in response to the vessel wall washing effect or clotting.
Thus, what is needed is an improved catheter configuration for use in extracorporeal treatment of body fluids such as dialysis. In particular, what is needed is a catheter configuration that is structured and arranged in a manner to inhibit recirculation of treated fluid for retreatment. Further, the catheter configuration is structured and arranged in a manner to ensure that inflow and outflow ports are not restricted in any appreciable way so that extracorporeal fluid treatment is more effective.